A method of using a catalyst is known as a production method of a polyolefin. For example, where 1-hexene is used as a raw material olefin, a linear low density polyethylene (LLDPE) is obtained.
On the other hand, trimerization reaction of ethylene using a chromium series catalyst is known as a production method of 1-hexene. The representative chromium series catalyst is a chromium series catalyst comprising a combination of at least a chromium compound (a), a nitrogen-containing compound (b), an aluminum-containing compound (c) and a halogen-containing compound (d) (for example, see Patent Document 1).
Trimerization reaction of ethylene is conducted in the presence of a reaction solvent. After completion of the reaction, 1-hexene obtained is treated in a distillation column, and separated and recovered from the reaction solvent. In such a case, 1-hexene may contain a slight amount of an organohalide.
Conventionally, an organohalide in 1-hexene is removed from the fear that the organohalide adversely affects a catalyst for linear low density polyethylene production (single-site catalyst). From long ago, various methods are known as the removal method. For example, a method of using an ion-exchange resin (see Patent Document 2) and a method of using an adsorbent such as alumina, silica, silica-alumina or activated clay (see Patent Document 3) are known. Additionally, a method of using zeolite having a pore size of 5 angstroms or more as an adsorbent is known as a method which is improved so as to remove under mild conditions. By this method, 2-chlorobutane in 1-hexene is removed up to 0.1 ppm by weight or less (0.04 ppm by weight or less in terms of a chlorine atom) (see Patent Document 4).
Patent Document 1: JP-A-11-060511
Patent Document 2: JP-A-53-103411
Patent Document 3: JP-A-57-183726
Patent Document 4: JP-A-3-99024